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  Difference between ConcurrentHashMap and Hashtable

Both ConcurrentHashMap and Hashtable are Collection classes for storing key value pairs and they both provide fast element search with a supplied key. They have much in common. However, we will not discuss the similarities between them here, instead we will focus on the differences between them. ConcurrentHashMap and Hashtable are both thread safe. But the mechanism for thread safe is different between them. Hashtable is synchronized, it utilizes the synchronization mechanism; while ConcurrentHa...

   ConcurrentHashMap,Hashtable     2013-11-18 08:06:54

  Encrypting and decrypting PGP file or text on MacOS

When doing data exchange among different parties, there is a frequent need of encrypting data or file and sending it to partner and asking partner to use corresponding key to decrypt the data or file. A famous way of exchanging data is using asymmetric keys where no secret key needs to be shared. One party can just use the public key shared by partner to encrypt the data and the other party uses the private key to decrypt the data. Today, we will introduce how to use PGP to encrypt and decrypt d...

   TUTORIAL,ENCRYPTION,DECRYPTION,PGP,GPG     2020-10-29 05:06:09

  Undefined property or variable in JavaScript

JavaScript is a weak type language, and also you can use a variable or property where it's undefined. If we don't have correct ways to check whether a property or variable is defined, we may get unexpected results when we try to access the,. How can we check whether a property or variable is undefined? This is actually a somewhat tricky question. Let's start off with some facts about undefined and then see what kind of function is consistent with the ones we care about. JavaScript attaches type...

   Property,Undefined,Array,JavaScript     2014-07-24 06:56:07

  37 powerful Linux shell commands

To work on Linux platform, you cannot avoid using shell commands to complete some tasks. These tasks can be as simple as list files in some directories or find some text in some file, or can be as complex as monitoring processes. In this post, we will share 37 powerful Linux shell commands.   Task Commands 1 Delete file with 0 byte(empty file) find . -type f -size 0 -exec rm -rf {} \;find . type f -size 0 -delete 2 Check process memory consumption ps -e -o "%C : %p : %z : %a"|sort -k...

   Linux command,List     2013-09-16 07:47:16

  Why does LinkedIn migrate to NodeJS from Ruby?

Node.js, the server-side JavaScript-based software platform used to build scalable network applications, has been all the rage among many developers for the past couple of years. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices. Because of these advantages, there are many websites are migrating to Node.js.One of them is LinkedIn. LinkedIn was initially built on Ruby...

   LinkedIn,NodeJS,Ruby     2014-03-21 23:39:25

  A trap in PDOStatement::bindParam

First, let's check out below codes: <?php $dbh = new PDO('mysql:host=localhost;dbname=test', "test"); $query = <<prepare($query); $bind_params = array(':username' => "laruence", ':password' => "weibo"); foreach( $bind_params as $key => $value ){ $statement->bindParam($key, $value); } $statement->execute(); What is the SQL executed finally? Is there any problem with above codes? Many people may think the query executed is : INSERT INTO `user` (`username`, `password...

   PHP,Trap,bindParam     2013-08-29 10:48:55

  Difference between keystore and truststore

Security has become a vital concern in most of the online transactions nowadays. Lots of the world's most popular websites have adopted security protocols to transfer data, especially sensitive data. These security protocols including SSL/TLS which are using the private/public key exchange mechanism to establish secure connections.  The private/public key cryptography is a really important invention and it allows data to be transferred securely and solves the big problem of transferrin...

   KEYSTORE,TRUSTSTORE,SECURITY,SSL     2017-03-04 07:52:47

  Resolving SVN error "Error validating server certificate for..."

When using SVN to connect secure server, the server needs to send its certificate to the client for verification. In some cases, the certificate sent by the server is not a trusted certificate, the client may choose to trust the certificate if the server is target server for sure.  But users may get "Error validating server certificate for 'https://...'" the next time when they try to connect to the same secure server even if they specified "p" the first time when they are prompted to accep...

   SSL,SVN,SVN.SSL.SERVER     2016-06-27 07:36:49

  Why Microsoft chooses Alt+F4 to close a window

For a long time, there is a doubt among lots of Windows users especially those English speaking users, that is why Microsoft chooses Alt+F4 to close a window instead of Alt+Q. Alt+Q is more comfortable to press for many keyboards, also Q represents Quit and it is easier for people to understand. Recently Microsoft answered this doubt. Raymond Chen, longtime Microsoft developer and semi-official Windows historian, said the reason is that not everyone speaks English. It d...

   WINDOWS,MICROSOFT,HISTORY,ALT+F4     2016-02-23 09:56:41

  Different types of keystore in Java -- JKS

JKS is Java Keystore, a proprietary keystore type designed for Java. It can be used to store private keys and certificates used for SSL communication, it cannot store secret keys however. The keytool shipped with JDKs cannot extract private keys stored on JKS. This type of keystore usually has an extension of jks. Next we will show how to operate the JKS keystore with pure Java code. Create JKS keystore The simplest method to create a JKS keystore to create an empty keystore. We can first get an...

   DEMO,EXAMPLE,KEYSTORE,JKS     2014-09-05 20:21:51

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